1. Field of the Invention
The present invention relates to petroleum production wells. More particularly, the invention relates to well completion and production methods and apparatus.
2. Description of the Prior Art
The process and structure by which a petroleum production well is prepared for production involves the steps of sealing the production zone from contamination and securing production flow tubing within the well borehole. These production zones are thousands of feet below the earth""s surface. Consequently, prior art procedures for accomplishing these steps are complex and often dangerous. Any procedural or equipment improvements that eliminate a downhole xe2x80x9ctripxe2x80x9d, is usually a welcomed improvement.
Following the prior art, production tube setting and opening are separate xe2x80x9ctripxe2x80x9d events. After a well casing is secured by cementing, a production string is then positioned where desired within the borehole and the necessary sealing packers set. In some cases, the packers are set by fluid pressure internally of the tubing bore. After the packers are set, a cementing circulation valve in the production tube assembly is opened by tubing bore pressure, for example, and annulus cement is pumped into position around the production tubing and above the production zone upper seal packer.
This procedure leaves a section of cement within the tubing below the cementing valve that blocks the upper tubing bore from production flow. The blockage is between the upper tubing bore and the production screen at or near the terminal end of the tubing string. Pursuant to prior art practice, the residual cement blockage is usually removed by drilling. A drill bit and supporting drill string must be lowered into the well, internally of the production tubing, on a costly, independent xe2x80x9ctripxe2x80x9d to cut away the blockage.
An objective of the present invention is to position well production tubing within the wellbore, secure the tubing in the well by cementing, and open the tubing to production flow in one downhole trip. In pursuit of this and other objectives to hereafter become apparent, the present invention includes a production tubing string having the present well completion tool assembly attached above the production screen and casing shoe.
This completion tool assembly includes an alignment of four basic tools in serial downhole order. At the uphole end of the alignment is a pressure actuated cementing valve followed by an external casing packer. Below the casing packer is a pressure actuated production valve and below the production valve is a bore plug landing collar
With the tubing string downhole and the open hole production screen located at the desired position within the well production zone, an opening plug is deposited in the tubing bore at the surface and pumped down the tubing bore by water, other well fluid or finishing cement until engaging a plug landing collar. Upon engaging the landing collar, the plug substantially seals the tubing bore to facilitate dramatic pressure increases therein. Actuated by a pressure increase within the tubing bore column, the external casing packer is expanded to block the borehole space annulus between the raw borehole wall and the packer body. An additional increase in pressure slides the opening sleeve of the pressure activated cementing valve into alignment of the internal and external circulation ports. Upon alignment of the circulation ports, tubing bore fluid such as cement is discharged through the ports into the wellbore annulus space. Due to the presence of the expanded external casing packer below the circulation ports, the annulus cement must flow uphole and around the tubing above the packer.
When the desired quantity of cement has been placed in the tubing bore at the surface, the fluidized cement within the tubing bore column is capped by a closing pump-down plug. Water or other suitable well fluid is pumped against the closing plug to drive most of the cement remaining in the tubing bore through the circulation ports into the annulus. At the circulation port threshold, the closing plug engages a plug seat on the closing sleeve of the pressure actuated cementing valve. With a first pumped pressure increase acting on the fluid column above the closing plug seat, the cementing valve closing sleeve slides into a circulation port blocking position.
With the circulation port closed, a second pressure increase that is normally greater than the first develops a force on the plug seat of such magnitude as to shear calibrated retaining screws that hold the seat ring within the tubing bore. When structurally released from the tubing bore wall, the closing plug and plug seat impose a piston load on the short cement column supported by the opening plug and plug landing collar. This column load is converted to fluid pressure on the pressure activated production valve to force a fluid flow opening through the valve. When the pressure activated production valve opens, the residual cement column is discharged through the open valve below the packer.
Although the residual cement column is discharged into the production zone bore, the absolute volume of cement dispersed into the bore is insignificant.
As the closing plug is driven by the finishing fluid through the central bore of the production valve past the valve opening, the finishing fluid, water or light solvent, rushes through the valve opening to flush it of residual cement and debris. At this point, a clear production flow path from the production zone into the production tubing bore is open. When pressure on the finishing fluid is released, upflowing production fluid sweeps the residual finishing fluid out of the tubing bore ahead of the production fluid flow.